Hi, This was an unusual beach find in Tampa Bay, Florida. I thought it was a vertebrae of some kind so I tossed it in my bucket. When I was going through my Florida Fossil book looking at horse teeth one day, I saw a horse ankle bone that resembled my find. It's very hard, light probably because it is hollow; but doesn't appear to be mineralized. I'm not sure it is a fossil, but I also don't know how it could be modern. What is it?